1. Field of the Disclosure
The disclosure is generally related to correction fluids. More particularly, the disclosure is related to stable correction fluids and to solvent-based correction fluids that change from colored to substantially white (or to a color substantially matching the substrate color) after application to a substrate.
2. Brief Description of Related Technology
Correction fluids are typically used to correct handwritten, typewritten, photocopied, and/or printed markings on paper, cardboard, glass, and other substrates. Correction fluids are usually applied to the substrates as liquids. The applied liquids subsequently dry to form an opaque film, which should be capable of (1) effectively covering and concealing any undesirable markings previously made on the substrate, and (2) being written upon such that it can ‘receive’ new corrected markings. The film should remain bonded to the substrate surface over time, and be sufficiently flexible such that the film will not crack or otherwise be displaced from the substrate during normal handling. Additionally, the film (and ideally, the liquid form of the correction fluid) should not interact with the ink composition of the corrected markings because such an interaction would likely cause discoloration of the film. Furthermore, the drying time of the correction fluid should be as fast as possible in order to allow corrected markings to be made over the film relatively soon after application of the correction fluid.
Correction fluids typically include an opacifying pigment (e.g., titanium dioxide), a film-forming polymer, and a solvent. The opacifying pigment is dispersed in the correction fluid, and allows the film to conceal any undesirable markings previously made on the substrate. The film-forming polymer is dissolved in the correction fluid, and allows the correction fluid to form a flexible, continuous film (or covering) that remains on the substrate once the solvent has evaporated. The solvent is the carrier for the opacifying pigment and the film-forming polymer, and can be either a volatile organic solvent or water. Volatile organic solvents have the advantage of evaporating quickly, and as a result, organic solvent-based correction fluids are often ready to receive corrected markings more quickly than water-based correction fluids. Water-based correction fluids are generally preferred for environmental reasons, however.
One problem associated with current correction fluids is that it is difficult for the consumer to determine when the correction fluid has dried sufficiently. Consequently, the consumer is forced to employ a trial and error technique to determine if the fluid has sufficiently dried. If the consumer attempts to make written marks over an insufficiently dried film, the writing point of the consumer's writing instrument will likely disrupt film formation by penetrating the partially-dried film. Disrupting film formation in this manner often causes some undesirable markings, which were intended to be concealed and covered by the applied correction fluid, to become visible and at least partially uncovered. Thus, when a consumer writes over an insufficiently dried film, the consumer must often apply an additional coat of correction fluid over the uncovered undesirable markings, wait for the applied correction fluid to dry sufficiently to form a film that can receive a written mark, and again make corrected written marks over the film. Additionally, disrupting film formation often causes the final film to have an especially uneven or unsmooth surface, which can be unsightly, particularly after receiving written markings thereover.
One solution to the problem of determining when a correction fluid has sufficiently dried so as to allow marking to be made thereover is described in Japanese Patent No. JP 6049397, which discloses a correction fluid including an opacifying pigment, water, a volatile organic solvent such as ethanol or acetone, and a reagent that changes from a first color to a second color, which allegedly occurs substantially simultaneously with the completion of solvent evaporation. The color-change of the disclosed formulations is caused by reaction with air. In one formulation, the color-change is caused by absorption of ambient carbon dioxide. In another formulation, the color-change is caused by air oxidation. In both formulations, the color-change reactions are slow and unreliable, and are not directly related to solvent evaporation (and thus sufficient drying of the correction fluid).
Commonly owned and copending U.S. patent application Ser. No. 10/776,860, which published as U.S. Patent Publication No. 2005/0075419 on Apr. 7, 2005, and which is incorporated herein by reference in its entirety, discloses a water-based color changing correction fluid. However, although water-based correction fluids are often more environmentally friendly than organic solvent-based correction fluids, the drying time and the covering ability of water-based correction fluids (the latter deficiency being of particular concern for water soluble dye containing water-based inks as bleeding of the ink into the applied correction fluid often occurs) are often not satisfactory. Furthermore, it has been difficult to utilize the color changing chemistries applied in water-based correction fluids to solvent-based correction fluids.
The opacifying pigments contained in correction fluids can settle over time, and therefore correction fluids must often be mixed before being applied to a substrate. Many application systems, for example, bottle and brush correction fluid systems and bottle and foam applicator correction fluid systems, allow the consumer to mix the contained correction fluid, as necessary. Conventional capillary-action markers contain a fibrous reservoir and a nib in fluid communication therewith, and therefore do not allow correction fluids contained therein to be effectively mixed. Further, the marker's reservoir fibers can undesirably filter any opacifying pigments contained therein and become clogged over time. Accordingly, over time, the marker is generally rendered incapable of making corrective markings. Thus, it has also been particularly difficult to achieve capillary-action markers containing a correction fluid that is stable therein because such applicator systems do not accommodate mixing and can become clogged.